Allowing pervious versions of the files would be a bit complex for Wappler - I assume - because of the weekly releases. It would require a lot of meta-data to allow switching version of your project or even downgrading Wappler itself.
One of the reasons could also be that you build something with some new feature, and then when you want to downgrade, it would crash your application.
TLDR: Use Git. Keep backup of Wappler installation files.
Git is the best option to tackle this. You know exactly what is being changed, and have the option to discard the changes.
Its scary to start using Git, specially in teams, but once you bit the bullet, go through a few iterations of hit-and-trial, you can never go back.
Since version 5 (I think), updating files using the project updater has made things a bit easier as well. With this, Wappler no longer updates the files automatically, so its under my control. And when I do update, I can verify the changes with Git.
For worst case scenario, we have been keeping backups of Wappler installation file for Windows since 1.9.1 (one of the first cases where we faced a major problem after a Wappler update) and Mac Silicon since it started. 46.3GB and counting. So if you need any previous version, message me.